The present invention relates generally to distillation apparatus which utilizes or operates according to the so-called thermocompressor principle. More particularly, the present invention is directed to an improvement within such distillation apparatus.
Distillation apparatus which operate according to the so-called thermocompressor principle are known and generally comprise a housing in which a boiling chamber for accommodating the liquid to be distilled is situated, heating means for heating the liquid in the boiling chamber, feed line means for conducting liquid to be distilled into the boiling chamber, output line means for removing distillate from the distillation apparatus, and means for imparting additional energy to the vapor produced from the liquid in the boiling chamber such that the temperature of the vapor at the output side of the apparatus is increased. At least one heat exchange tube along which a mixture composed of liquid to be distilled and vapor flows, and a droplet separator based on centrifugal separation, are also provided within such distillation apparatus.
Conventional distillation apparatus utilizing the so-called thermocompressor principle generally operate as follows. The liquid to be distilled is heated in the boiling chamber whereupon it evaporates with the vapor moving into the upper portion of the boiling chamber and having a temperature of about 96.degree. C. The vapor so produced is drawn from the upper portion of the boiling chamber into a compressor which imparts additional energy thereto whereupon the temperature of the vapor increases at the output or delivery side of the compressor to about 105.degree. C. The vapor (e.g. steam) at the increased temperature is then conducted into a helical tube through the boiling chamber whereupon the vapor condenses into distillate whereupon the distillate is removed from the distillation apparatus. The condensing vapor naturally releases at least a portion of its heat energy to the liquid to be distilled accommodated within the boiling chamber.
Although such conventional distillation apparatus which operate according to the thermocompressor principle described above have the advantage of relatively low energy consumption, e.g., about 4 kw per 100 liters/hour of liquid to be distilled, certain disadvantages are also inherent in such operation. The greatest drawback of such conventional apparatus is the admittance of impurities into the evaporated distillate falling through the compressor which of course prevents an absolutely pure distillate from being obtained. Moreover, such distillation apparatus of the prior art are exceedingly massive and bulky and create objectionably high noise levels during operation.
Improvements have been made in the conventional distillation apparatus which operate according to the thermocompressor principle as described above in that the temperature of the vapor produced in the upper regions of the boiling chamber is higher than 100.degree. C., usually about 105.degree. C., whereby the pressure in the boiling chamber will exceed atmospheric pressure. As a result thereof, the temperature of the vapor will increase to about 120.degree. C. at the output side of the compressor. However, in other respects, the various advantages and disadvantages of the improved distillation apparatus are the same as those discussed above in connection with the conventional distillation apparatus.
Also known in the art is distillation apparatus which operates in accordance with the thermocompressor principle and wherein the temperature of the vapor produced from the liquid to be distilled is increased utilizing a heat pump. In this arrangement two separate heat exchangers are utilized, one heat exchanger being situated in the upper region of the boiling chamber while the other heat exchanger is situated in the lower region of the boiling chamber. However, this arrangement is expensive in manufacture and requires a complex control mechanism for its operation.
U.S. Pat. No. 4,421,605, issued Dec. 20, 1983, also discloses a distillation apparatus operating on the thermocompressor principle including a housing in which a boiling chamber for accommodating the liquid to be distilled is situated, means for heating the liquid within the boiling chamber, feed line means for conducting liquid to be distilled into the boiling chamber, output line means for removing distillate from the distillation apparatus, and means for imparting additional energy to the vapor produced from the liquid within the boiling chamber, so that the temperature of the vapor at the output side of the apparatus is increased. In order to obtain distilling apparatus operating on the thermocompressor principle with simplified control technology, requiring little fluid volume, providing for quick initial heating of liquid to be distilled, providing for efficient droplet separation from vapor, producing distillate of excellent quality and purity, and consuming little energy and being small in size and simple in construction, at least one heat exchange tube along which a fluid composed of liquid to be distilled and vapor is arranged to flow, and a droplet separator based on dynamic centrifugal separation are both provided within the distillation apparatus. The droplet separator is situated within the distillation apparatus in a manner to define a gush or overflow gap between the same and a wall of the boiling chamber through which the mixture of liquid to be distilled and of vapor is adapted to flow after the mixture has discharged from the heat exchange tube.
After the mixture of the liquid to be distilled and the vapor is discharged from the heat exchange tube and has flowed through the gush or overflow gap with the vapor having flowed through the droplet separator, the vapor is then directed into the means for imparting additional energy to the vapor. According to a feature of the apparatus disclosed in U.S. Pat. No. 4,421,605, the additional energy imparting means is constituted by blower means situated within the distillation apparatus, and the droplet separator is provided with helical vanes and is connected to a lower face of the blower means. Waste pipe means are provided through which a portion of the liquid to be distilled is discharged from the boiling chamber in a continuous manner to stabilize the level of liquid within the boiling chamber. Also, the heat exchange tube extends through a vapor condensation chamber and is situated around the boiling chamber, with heating means, by which the liquid to be distilled is heated within the boiling chamber, being situated below the heat exchange tube. Drive means for the blower means is a motor with a short-circuited rotor that is fitted to drive the blower means by magnetic transmission through an end wall of the distillation apparatus.
Although excellent in structure and in operation, the distilling apparatus of U.S. Pat. No. 4,421,605 is still encumbered by certain drawbacks. Initially, the return flow of vapor from the compressor to the condensor is unsatisfactory, since vapor has to be directed in a complicated manner through "water wells". It is also necessary to circulate the effluent, with the result that the structure of the distilling apparatus becomes contaminated. Moreover, the blower means which imparts additional energy to the vapor has been disposed at the upper end of the distillation apparatus in U.S. Pat. No. 4,421,605, which results in a comparatively massive structure and inconvenient, difficult maintenance.